15.3 Process technology (Figure 15.1)

Figure 15.1 Flow sheet of Hydrocarbon Steam Cracking for Petrochemicals

• • Naphtha/LPG saturates is mixed with superheated steam and fed to a furnace fuel gas + fuel oil as fuels to generate heat.  The superheated steam is generated from the furnace itself using heat recovery boiler concept.

• The C₂-C₄ saturates are fed to a separate furnace fed with fuel gas + fuel oil as fuels to generate heat.

• In the furnace, apart from the steam cracking, steam is also generated. This is by using waste heat recovery concept where the combustion gases in the furnace.

• After pyrolysis reaction, the products from the furnace are sent to another heat recovery steam boiler to cool the product streams (from about 700 – 800°C) and generate steam from water.

• After this operation, the product vapours enter a scrubber that is fed with gas oil as absorbent. The gas oil removes solids and heavy hydrocarbons.

• Separate set of waste heat recovery boiler and scrubbers are used for the LPG furnace and Naphtha steam cracking furnaces.

• After scrubbing, both product gases from the scrubbers are mixed and fed to a compressor.  The compressor increases the system pressure to 35 atms.

• The compressed vapour is fed to a phase separation that separates the feed into two stream namely the vapour phase stream and liquid phase stream. The vapour phase stream consists of H₂, CO, CO₂ C₁-C₃+ components in excess.  The liquid phase stream consists of C₃ and C₄ compounds in excess.

• Subsequently, the vapour phase and liquid phase streams are subjected to separate processing.